Glass manufacture



Filed Sept. 1L, 1943 M l EA/I'OR SFMUEL James 54/517577;

Patented Mar. H2, 1946 hairs!) s'rA'rEs aATEN'r prams assess;

amass mnumcruas Samuel James Everett, Thornton Heath, England,

assignor to James A. Jobling & Company Limited, Sunder-land, England, a British company Application September 11, 1948, Serial No. 502,009 in Great Britain February 8, 1941 (Claims.

say, surfaces that are absolutely true and smooth with the fine quality that can be obtained by grinding and lapping or polishing. Glass tubing made either from ordinary glass or from low-expansion glass and having the qualities obtainable by making use of the present invention can conveniently be employed as cylinders for hypodermic syringes.

The invention is carried into effect by the adaptation of a known method of manufacturing glass tubing in which a ribbon of molten glass is poured on to a refractory mandrel which is set at an angle and slowly rotates at from four to ten revolutions per minute. The glass is drawn in tubular form from the lower end or the mandrel and becomes gradually less plastic as it travels away until, at a point which is from about ten to fifteen feet from the mandrel, the glass is cool enough to become rigid. Substantially at this point the tubing reaches a series of asbestos covered rollers over which it travels for about fifty to one hundred feet to a point where it is cut up into lengths.

The cross-sectional dimensions, however, such 1 other hand, enables tubing having very accurate cross-sectional dimensions to be produced. The adaptation is effected by passing the tubingover an accurately shaped former located at the point where the tubing is in a semi-plastic condition so that the internal or external diameter of the tubing is accurately controlled whilst the final setting of the glass takes place.

The present invention therefore comprises a method of forming a tube with a fine quality internal surface, said method including the features of delivering a ribbon of molten glass to a rotating refractory mandrel, withdrawing said glass in tubular form from said mandrel, passing said glass-tubing over a former located at the point inside said tubing and remote from said mandrel where the glass is in a semi-plastic condition, and rotating said former about the axis of said tube.

The invention also includes apparatus for forming a glass tube with a fine quality internal surface, said apparatus comprising in combination a refractory mandrel, means for rotating said mandrel, means for delivering a ribbon of glass on to said mandrel, means for withdrawing the glass in tubular form from said mandrel, a former located remote from said/mandrel to lie inside the glass tube at a point where the glass is semiplastic, and a flexible driving connection for rotating said former about the axis of said tube and extending through said mandrel.

In order that the invention may be clearly understood and readily carried into effect a specific 'example thereof will now be described with reference to the drawing in which:

Fig. 1 is a sectional diagrammatic elevation of apparatus shown in the process of manufacturins a glass tube, and

Fig. 2 is a diagrammatic perspective of a modified construction of the former. I

The glass tube is formed directly from a ribbon it of molten glass delivered from a suitable heated container 52 to a refractory mandrel 53 which, in practice is approximately two feet long, eight inches in diameter, and set at an angle of about seven degrees to the horizontal.

This mandrel is positively driven so that it rotates about its axis at from four to ten revolutions per minute. The glass is drawn in tubular iorm from the lower end of the mandrel 53 and becomes gradually less plastic as it travels away until, at a point which is about ten to fifteen feet from the mandrel 53, the glass is cool enough to become rigid.- Substantially at this point the tubing reaches a series of asbestos covered rollers, two such rollers 54 being indicated in the drawing. These rollers serve to provide the necessary drawing action and the glass tubing 50 travels over them for about fifty to one hundred 'feet to a point where it is cut up into lengths The tubing travels horizontally over the rollers so that, the plastic glass in passing from the inclined mandrel 53 to the rollers follows, under the force of gravity, a gently curved path. The inventive feature in this arrangement consists in passing the tubing over an accurately shaped rotating former 55, located at a point where the tubing is in a semi-plastic condition, so that the internal surface of the tubing is accurately controlled whilst the final setting of the glass takes place. The former 55 is rotated about its axis at a speed of approximately revolutions per minute so as to produce an internal here which is quite round, free from wrinkles and has the appearance of being polished as well as having precisel y the required diameter. The former 55 is mounted st the end oi e, metal tube to extend lug upwards through the cod port of the gloss tube and through the rotot refractory sudrei $53. The former is driven be e flexible vine element 5? inside the motel tube end extending between the former sud suitable driving means. The driving element St may be of any known construction, such as e heir of? coma centric helicslly wound best resisting wires wound in opposite directions, or e series oi uni: versolly jointed members. The former itself is made of pure silica, stainless steel or the nickelchromium motel silos moonell.

The drawing of the glass tube is not started with the former Ell in position, but when the drewing has been begun, the former assembly, in: cluding the flexible driving element El and the motel tube E36, is passed into position through a. central passage be the slowly roteting relroctory mandrel 53. A pipe constitutes an ex tension 01 this passage end is used to con== vey air which is blown through the meudrei into the glass tube to prevent it item coliepsing when in s plastic state.

In order to lubricate the glass tube as it posses in a, semi-plastic state over the former 55, graph its in powder form or other suitable lubricant, such as lead oxide, may be carried in suspension by the air that is blown into the gloss tube. Al-

' ternetively, a jet of air carrying lubricating powder may be blown down the metal tube and discharged; at the periphery oi the former so as to blow the lubricstlng powder on to the contacting surfaces respectively of the dormer and glass tube. It is to be understood that the plasticity of the gloss and the speed of drawing in the vi clnity of the former 65 is such thet the air pres= tot ed by an suitable means. Kn the drewirig such mesnshas been diogrammeticully shown as comprising e worm wheel 69 secured to the she-lit and adapted to be driven by a worm Eli rotated by a motor or other means (not shown). Simi= larly, the tube 8% may be rotated by e worm gear 62 and worm so driven by any suitable motive force.

In Fig. i there is also shown schematically a nozzle 65 for supplying sir or sir with lubricating powder suspended therein as described here u, it being understood that the nozzle 86 directs into the tube 58.

The rotating former as shown in fig. 2 may be provided with a narrow fist surface along one side so that the cross-section or the former appears as o circle with a; smell segment removed,

I claim:

1. Apparatus for forming a glass tube with a. fine quality internal surface, said apparatus comprising, in combination, e, refractory mandrel, means for rotating said mandrel, means for deiivering a, ribbon ofgless on to said mandrel, means for withdrawing the glm in tubular form from said mandrel, a, former locsted remote from said mandrel to lie inside the glass tube at a point where the glass is semi-plastic, and a driving connection for rotating said former about the ends of said tube and extending through said mandrel.

2, Apparatus for forming a glass tube with s time quality internal surface, said apparatus comprising, in combination, a mandrel, means for rotating said mandrel, means for delivering a ribicon of glass on to said msndrel, means for withdrawing said glass in tubular form from said mandrel, at former located remote from said man drel and disposed inside said glass tube at at point where said glass is send-plastic, end a driving connection for rotating said former about the axis of said tube. 

